1. Field of the Invention
The present invention relates to a manually-operated hand truck. More specifically the present invention relates to a hand truck which is provided with a mechanical or hydraulic type of servo device that allows cylinders which are loaded onto the hand truck to be lifted to a height suitable for transfer onto scales or the like type of apparatus.
2. Description of the Related Art
FIGS. 1 and 2 show two different types of currently available dollies and hand trucks for handing heavy loads and compressed gas cylinders.
The hand truck shown in FIG. 1 includes a frame 10 which is supported by two wheels 12, 12 and arranged to have a shelf-like platform member 14 which rests on the ground when the device is titled forward to an upright position. With this type of hand truck, it is possible to transport different loads from one point to another. However, once this type of the hand truck is tilted back to a position wherein an operator can walk it forward, the weight of the load which is supported on the platform 14 tends to produce a moment of force that tends to force the handle portion 16 of the frame 10 toward the ground. The operator is therefore obliged to control the angle at which the hand truck is tilted during motion in order to avoid strain on his or her arms. Further, this type of hand truck or cart is not particularly suited to transporting cylinders of compressed gas due to the possibility of the operator loosing grip of the handle 16 and allowing the hand truck to fall with the result that upper ends of cylinder may hazardously strike against the ground.
Under these circumstances, a hand truck of the nature shown in FIG. 2 is preferred in that, after a long object such as a gas cylinder 20 is loaded onto the platform 22 and the hand truck is pulled back to an angle at which forward motion is possible, the rear casters 24 contact the ground and limit the amount of rotation through which the frame 26 can be induced by the weight of the load.
However, while this device is simple and solves the drawbacks encountered with the type of truck shown in FIG. 1, a problem is encountered when moving a cylinder 20 from a storage site or the like to a set of scales to check the weight of the cylinder 20 such as is required when checking if the cylinder 20 contains the correct amount of gas. That is to say, the platform of the scales is usually above the level of the floor and it is usually required that the cylinder be off-loaded from the hand truck and then manually manhandled onto the scale platform by rolling the cylinder along its lower edge up a small ramp. After the weighing operation, the reverse process is necessary.
As will be understood, this process can be quite hazardous in that the cylinder must be tilted at an angle in order to roll the cylinder up and down the ramp. Under these conditions, the heavy and awkward-to-maneuver cylinder can cause back injuries or worse still, may be dropped with the risk of damaging the cylinder and risking uncontrolled release of compressed gas.